The present invention relates to an ink jet cartridge, in particular for supplying ink to an ink jet head of a recording apparatus, comprising a vacuum producing material inside a cartridge body which is provided with a communication opening for discharging the ink from the vacuum producing material and with a venting hole for balancing the pressure inside and outside of the jet cartridge body.
Ink cartridges are used in ink jet applications for computer printers, plotters, copying machines, facsimile machines or any other related recording apparatus and office equipment. During the application, the ink cartridge is fixed to the printing machine and is connected to the print head unit of the machine. The ink cartridge, thus, supplying ink to the print head to enable the machine to print characters or images. The ink cartridge body forms as container for storing the ink. The ink is held in the container by means of a vacuum producing material such as foam or foam pads of synthetic resin, respectively occupying the internal space of the cartridge body either partially or entirely. When the ink in the cartridge has been consumed the cartridge will be disposed of. The useful life of the cartridge is determined by the amount of ink that can be stored into the cartridge before use and the ink remaining in the cartridge as being held by the foam material after use. The ability to hold and retain ink in the cartridge, thus, substantially depends on the porousity or density of the foam material, which simultaneously, has the function of metering the ink to control the flow rate of the ink entering into the print head unit of the printing machine. In order to prolongate the life time of a cartridge it is the aim to store as much ink as possible in the cartridge and to minimise the the amount of ink retained in the cartridge, which can no longer be discharged towards the printing head due to the material-imminent and unavoidable remainder storage capacity of the foam.
Conventional ink cartridges use a single density foam pad to serve both ink storage and appropriate control of the ink flow rate. In order to assure a good metering of the ink flow the use of higher density foam is advisable. However, in such a case the ability of the foam pad to store greater amounts of ink is affected as the interior space of the cartridge body is completely occupied by the high density foam which is undesirable from the viewpoint of providing a high ink storage capacity. Moreover, high density foam retains more ink and, therefore, the quantity of non-useable ink is relatively high. Accordingly, the efficiency of ink useage in case of such a cartridge is low and further shortens the useful printing life of the cartridge.
Other conventional high capacity ink cartridges do not use any foam pads to hold the ink inside the cartridge body. In such cases the whole container body, thus, is filled with ink only. However, complicated air pressure balancing elements have to be integrated in order to be able to control the flow rate of the ink. An example of such a system uses a flat spring loaded airbag pressure control system. These pressure control systems are complicated and add to the costs of such a cartridge. Moreover, mass production is difficult.
From GB-A-2 268 910 an ink supply system for jet printers is known having an ink supply cartridge, which comprises two chambers which are interconnected by a narrow passage with one of the chambers being vented to the atmosphere at a point above the interconnecting passage and contains a capillary material which will withdraw ink into itself while the other chamber does not have any capillary filling. While such a system combines some advantages in view of the metering capabilities of a foam-filled cartridge body with those of a high ink storage capacity using a ink storage chamber without any foam material therein, also with such a system the manufacturing costs increase and difficulties in an undesirable leakage of the ink may occur.
Accordingly, it is an objective of the present invention to improve an ink jet cartridge as mentioned above in that it should combine high ink storage capabilites with a reliable preventing of leakage of ink and optimal ink metering capabilities by controlling the ink flow rate appropriately. Moreover, by increasing the difference between the big amount of ink storable at the beginning of print and the retained minimum amount of ink at the end of operation, a long print life and efficient useage of the ink should be assured through the ink jet cartridge.
In order to perform the aforeindicated objectives the present invention improves the ink jet cartridge in that the jet cartridge body accommodates at least two vacuum producing materials of different vacuum producing capacities.
According to a preferred embodiment the internal space of the jet cartridge body comprises two porous materials in contact to each other, said materials having different ink storage capabilities with the material having a higher vacuum producing capacity being disposed closer to the communication opening than the other vacuum producing material having a lower vacuum producing capacity. A communication opening is adapted to transfer the ink from the internal space of the cartridge body to the printing head.
According to yet another preferred embodiment of the present invention the vacuum producing materials are foams or foam pads of higher and lower foam densities, respectively.
In a preferred design of the ink jet cartridge according to the present invention the two foam pads of different foam densities are disposed side by side in the internal space of the cartridge body with the high density foam pad being in close proximity to the communication opening.
According to yet another preferred embodiment of the present invention, the two foam pads of different foam densities are disposed to contact each other, preferrably along a plane which extends in parallel to at least one wall of the cartridge body.
Thus, by means of filling the continuous interior space of the cartridge body with at least two vacuum producing materials of different vacuum producing capacities, preferrably by introducing a foam pad of high foam density in one part of the cartridge body adjacent to the communication opening, while the rest of the cartridge body is filled with a foam pad, of low foam density both a high ink storage capacity through the lower density foam pad and a high dispensing (i.e. metering quality and ink flow rate) control by means of the high density foam pad, which is disposed downstream of the low density foam pad, are achieved.
Thus, the ink cartridge has a cartridge body accommodating two different density foams or foam pads for the storage of the ink. The high density foam pad is used for metering the ink flow rate and for preventing leakage. The lower density foam pad is provided for storing a big amount of ink and for releasing the ink towards the high density foam pad easily. With the combination of both foam pads which are in contact to each other the ink jet cartridge assures a high amount of ink to be storable by the lower density foam pad and at the same time assures prevention of leakage as well as the ability to control the ink flow rate by the higher density foam pad. Thus, the cartridge can hold a big amount of ink at the beginning of the print and retain only a minimum amount of ink at the end of the use. Accordingly, the ink storage system, ie. the ink jet cartridge of the present invention comprises of at least two different vacuum producing materials having different vacuum producing capacities, specifically comprises two different foam pads of different foam densities in the cartridge body. The higher density foam is located nearer to the communication opening that is connected to the print head unit upon fixing the cartridge to a printing machine.
The purpose of the higher density foam is to control the ink flow rate to the print head unit and to create higher vacuum pressure to prevent ink from leaking through the communication opening hole. Moreover, all opening holes are properly sealed for transportation purposes to further eliminate any ink leakage. The sealing materials are detachable before using the cartridge.
The second foam pad with lower foam density is capable of holding a big amount of ink and to release ink to the first higher density foam pad downstream of the second lower density foam pad easily. The lower density foam is located distant from the communication opening hole with the first higher density foam being disposed between said communication opening hole and the second lower density foam pad.
Due to its lower density a second lower density foam pad is able to store a big amount of ink, but produces very little vacuum pressure to hold the ink. Therefore, all contact surfaces of the cartridge body that are in touch with the second lower density foam pad are fully sealed to eliminate the ink from leaking out of the cartridge body.
Preferrably only one surface of the lower densities sponge is in contact with the first higher density foam pad to enable the lower density sponge to supply ink to the first higher density foam.
The density and size of the first higher density foam pad is adapted to the specific operational needs the ink jet cartridge aims to meet for a proper control of the ink flow.
Preferrably the thickness of the first higher density foam pad is bigger than the internal width of the cartridge body, so as to create a tight contact through its sponge effect to the cartridge wall upon inserting the foam pad into the cartridge body. The tightness of the contact and the pressure towards at least two opposite walls of the cartridge bodies should ensure to hold the foam pad and to maintain its location upon inserting the cartridge body into a printing machine. This is to assist and ensure a proper contact of the higher density foam pad and the printing head unit in order to ensure a proper flow of ink.
Normally, an ink jet cartridge as indicated hereinabove is handled by an operator or office clerk and therefore it is always possible that strong forces are applied and deform the ink container wall causing the ink storing foam pads to be squeezed and to render the ink leaking out. Therefore, the thickness of the walls of the cartridge body must be properly designed taking the cartridge size as well as the type of plastic material for the cartridge body into consideration to gain sufficient rigidity of the cartridge.
Finally, it is preferred to provide lugs or internal projections, preferrably opposite ones raising from the inner walls of the cartridge body to establish additional abutting and holding means for the foam pads inside the cartridge body.
Further preferred embodiments of the present invention are laid down in the other subclaims.